Ship stabilizer



ay 14, 1968 E. v. LEWIS 3,382,834

SHIP STABILIZER Original Filed July 30, 1964 3 Sheets-Sheet l INVENTOREdward 1/. Lewis y 4, 1968 E. v. LEWIS 3,382,834

SHIP STABILIZER Original Filed July 30, 1964 5 sh t -s g INVENTOR EdwardV. Lew/s BY M l a A EYS United States Patent 3,382,834 SHIP STABILIZEREdward V. Lewis, Glen Head, N.Y., assignor to John J. McMullenAssociates, Incorporated, New York, N.Y., a corporation of New YorkOriginal application July 30, 1964, Ser. No. 386,197, now Patent No.3,269,345, dated Aug. 30, 1966. Divided and this application Mar. 17,1966, Ser. No. 559,013

4 Claims. (Cl. 114-125) ABSTRACT OF THE DISCLOSURE A passive freesurface tank stabilizer including therein a plurality of upstandingplates extending athwartship with with their ends spaced inboard fromthe tank ends to form wing tanks and spaced fore and aft to defineathwartship passageways interconnecting the wing tanks. Each plate hasroughened or corrugated surfaces to greatly damp tank liquid movementthroughout the length of the interconnecting passageways andsubstantially over the entire roll cycle.

This application is a division of application No. 386,- 197 filed July30, 1964, now Patent No. 3,269,345.

The present invention relates generally to a ship stabilizer and moreparticularly an improved apparatus for applying a restoring moment bythe movement of fluid Within a tank Ships of practically every typeencounter the problem of undesirable ship motion caused by the surfacecondition of water. Depending upon the type and size of the ship and theoperating conditions to which the ship is to be subjected, various hulldesigns are selected to counteract the tendency of the water to impartmotion to the ship. Due to the great number of variables present andsince cyclic wave motion can cause a gradual increase in the energy ofmotion of the ship, hull design provides only a limited effect incontrolling the ship motion. Other attempts to minimize ship motion inresponse to wave action include the provision of stabilization systemswhich are capable of applying a restoring moment to the ship when it issubjected to the motion. Particular emphasis has been made with respectto improving systems for minimizing roll. Ballast tanks connected bypiping and the like have been employed in order to transfer water in amanner to generate a restoring moment, Such systems encounter thedifficulty of maintaining the proper phasing between the restoringrnoment and motion imparted to the ship. Eflorts to employ volumes ofair above liquid ballast for controlling the ballast have resulted inmassive systems which are uncertain as well as excessively noisy inoperation. Efforts have also been directed to providing the ship withfin members extending from the hull beneath the water line and adaptedto generate restoring moments from the hydrodynamic forces on the finsaccompanying the motion of the ship. In certain applications controlledfins have been effective in controlling the roll of the ship but onlywith the expense of complex systems employing massive fin members andoperating machinery. Furthermore, controlled fins are generallyeffective only when the ship is under way with suflicient speed to causedrag resulting in a loss of ship speed.

In the past, stabilization systems have been primarily used in ships inwhich it is desired to have stabilization only when the ship is underway. The problem of stabilizing a stationary ship now, however, is ofgreater importance. For example, ships carrying radio equipment foraircraft navigation purposes are conventionally wired to be maintainedon station in the mid-ocean for extended periods of time. Such ships maybe maintained at a stationary point or operated at low speed about astationary 3,382,834 Patented May 14, 1968 point. In defense systemsradar picket ships, which again operate at a predetermined station, areemployed to carry early warning radar equipment at extended distancesfrom land. In the development of missile devices and space vehicles, itis necessary to maintain great numbers of ships on station throughoutthe oceans of the World in order to track and monitor the flight andpath of operations of these devices. It is obvious that withoutsufli'cient degree of stabilization the equipment carried by any ofthese ships can be interferred with by excessive ship motion andrendered practically ineffective during a heavy sea condition.

Accordingly, it is the primary object of the present invention toprovide a ship stabilizer which is capable of applying a restoringmoment to the ship whether the ship is under way or stationary.

More particularly, it is an object of the invention to provide a shipstabilizer which is passive, that is, a stabilizer which applies therestoring moment directly in response to the movement of the ship aboutthe axis about which the ship is to be stabilized without the need ofcontrol equipment.

Furthermore, it is an object of the invention to provide a shipstabilizer in which the movement of fluid in response to the movement ofa ship is sufiicienly opposed in order that the fluid can apply arestoring moment to the ship.

Another object of the invention is to provide a ship stabilizer which ispassive in oeration but which is adapted to be conveniently adjusted tocompensate for changes in the condition of the ship or the sea.

A still further object of the invention is to provide a ship stabilizerwhich is relatively compact and of reasonable weight.

A further object of the invention is to provide a ship stabilizer whichdamps the movement of fluid therein so that better stability can beobtained and the degree of roll of the ship is held to a minimum.

In one embodiment of the invention the ship stabilizer comprises a tankcontaining a quantity of fluid having a free surface. The longitudinalaxis of the tank is adapted to extend substantially horizontally andsubstantially at right angles to the axis about which the ship is to bestabilized. Thus, if the ship is to be stabilized against roll, the tankis disposed in a substantially athwartship direction along one of thedecks of the ship. -In order to oppose the flow of fluid from oneportion of the tank to the other in response to the movement of theship, a plurality of flanges mounted on baffles are positioned in thetank for the purpose of impeding the flow of fluid in response to theroll of the ship. Said flanges and battles also provide for dampingkinetic energy of the mass of fluid arriving at the end of the tank todiminish the emission of a reflected wave therefrom.

One illustrated embodiment of the present invention has substantiallyuniplanar baflles with a plurality of flanges mounted thereon. Anotherillustrated embodiment of the invention has parallel baflle sectionsrunning in a zigzag course with flanges mounted at the extremitiesthereof. Still another embodiment of the invention has two parallel,stiffened, uniplanar plates mounted on either side of a stiffenedcorrugated plate. Yet another embodiment uses a plurality of uniplanar,stiffened plates having greatly corrugated or greatly roughenedsurfaces.

Other objects and features of the invention will become apparent in thefollowing specification and claims in view of the drawings in which:

FIGURE 1 is a vertical section view showing the stabilizer extendingacross the ship below the decks;

FIGURE 2 is an enlarged plan view of the stabilizer showing the tank andthe uniplanar baffles with the flanges mounted thereon;

FIGURE 3 is a sectional view taken along lines 3-3 of FIGURE 2;

FIGURE 4 is a perspective view of the embodiment shown in FIGURES 2 and3;

FIGURE 5 is a plan view of a modification which includes baflles thatrun in a zigzag course;

FIGURE 6 is a side elevation sectional view taken along lines 66 ofFIGURE 5;

FIGURE 7 is a plan view of another embodiment showing baflies mounted oneither side of a corrugated plate;

FIGURE 8 is a sectional view taken along lines 88 of FIGURE 7;

FIGURE 9 is a plan view of another embodiment illustrating a pluralityof greatly corrugated plates;

FIGURE 10 is a side elevation section taken along lines 1010 of FIGURE9;

FIGURE 11 is a plan view of yet another embodiment of the inventionshowing a plurality of roughened plates; and

FIGURE 12 is a side elevation section taken along lines 12-12 of FIGURE11.

Referring to the figures in detail, there is shown in FIGURE 1 a shipslabilizer generally indicated as siabi lizer 10 mounted athwartshipbelow decks 12 of ship 14. It can be seen, when the stabilizer 10 ispartially filled with fluid, said stabilizer can perform passivestabilization whenever roll forces are applied to ship 14. Thestabilizer comprises a tank 16 formed by sides 18 and 2t) and ends 22and 24. Tank 16 can have a top to prevent fluid spill; or the sides ofthe tank can extend between two decks, thus using the upper deck as atop. By extending the stabilizer across the hull of ship 14 the maximummoment arm for the liquid can be obtained. The stabilizer isproportioned in a manner such that the weight of the liquid which isdisplaced in a position adjacent an end portion thereof is suflicient togenerate a restoring moment capable of restoring the motion of the shipfor a range of sea conditions. The fluid within the tank has a freesurface and can move in response to the motion of the ship. It can beseen, however, that once the moment force is created by the liquid tooppose the roll of the ship, the fluid mass velocity increases so thatthe fluid mass begins to move across the tank to the Opposife endthereof. As wil be described below, a portion of the kinetic energy ofthe moving rnass will be absorbed by the flanges and plates so that alarge reflected wave will not result. To increase the frictional forcesand damping forces applied to the liquid, flanges '30 are mounted onboth sides of the plates 26 and 28.

Thus it can be seen that any movement of the fluid resulting from a rollof the ship results in fluid friction, local turbulence and fluidimpedance in the fluid imparted thereto by plates 26 and 28 and flanges30 mounted thereon.

The fluid to be employed within the stabilizer can be 1 any liquid orthe like having sufficient density and with a viscosity of asufliciently low magnitude so that flow can readily take place betweenthe flanges '30 and the plates 26 and 28. Liquids such as sea water,fresh water, bunker oil or types of liquid cargo can be used in thestabilizer tank. Once the stabilizer has been designed and installedwithin the ship, the depth of fluid within the stabilizer can be variedfor tuning the stabilizer to various conditions of the ship and sea.

In order for a restoring moment to be generated, it is necessary thatthe moment be substantially out of phase with the forces applied to theship by the sea. Thus, it the case of roll, as the crest of the wavestrikes along one side of the ship, the force resulting from the momentmust be applied in opposition to the force of the wave. After the wavecauses the ship to roll, it is necessary that the moment be reversed sothat the force is applied to the opposite side of the ship.

Operation of the stabilizer will now be described. Let it be assumedthat a wave strikes the ship such that the ship rolls to elevate side 32and lower side 34. As side 32 rises, the friction imparted to the waterby plates 26 and 28 and flanges 30 oppose the flow of the fluid from endportion 36 in the direction toward end portion 38. As side 32 approachesits maximum point of upward movemerit, a hydrostaiic head is formedwithin the stabi'izer so that flow passes in the direction of endportion 38. The potential energy of the fluid is maximum at the maximumelevation of side 32. The potential energy of the fluid in end portion36 is converted into kinetic energy as the fluid mass begins to flowtoward end portion 38. After side 32 is lowered and the ship passesthrough a level posiiion, the fluid continues to flow in the directionof end portion 38 due to its kinetic energy. In this way it is seen thatthere is an accumulation of fluid in end portion 38 as the portion ofthe hull adjacent thereto attempts to be eievated by the sea or rollingforces. As the mass of fluid arrives at end portion 38, a portion of thekinetic energy thereof is absorbed by the flanges 30 and plates 26 and28, and an impedance to a reflected wave is also imparted to the fluidby said flanges and plates. Also, the flanges 30 associated with plates26 and 28 in the vicinity of end portion 38 retard or impede animmediate reversal of flow as side 34 of the ship rises so that fluidcan present a restoring moment in opposition of the rising side 34. Thisprocess then continues so long as sea forces are applied to the bull tocause it to move about and roll about the axis of the ship.

It should be understood that the number of plates, such as 26 and 28,can be increased and the number and sizes of the flanges 30 can bechanged without departing from the spirit of the present invention.

Referring now to FIGURES 5 through 7, there is shown a stabilizing tank46 and mounted therein two upstanding plate members 48 and 50, eachhaving four sections 52, 54, 56 and 58, disposed in angular positions.Each corresponding section of one plate is substantially parallel tothat of the other. Mounted on sections 52 and 58 there is found flanges60 which function in the same manner as described above. The purpose ofthe zigzag path for plates 48 and 50 is to aid in the impedance anddamping processes, whereby the area of flow of the fluid is restrictedin areas 62, 64, 68 and 70 of tank 46. Also, the center passageway 72aids in the fluid impedance and damping by causing a number of changesof direction of fluid flow to dissipate energy.

It should be understood that the number of plates within tank 46 and thenumber of sections per plate and the number of and dimensions of flangesfound thereon may be varied without departing from the scope of thisinvention.

The embodiment of the invention shown in FIGURES 7 and 8 will now bedescribed. The stabilizer found in said figures comprises tank 74, inwhich vertically disposed plates 76 and 7 8 are mounted. An undulatingor corrugated plate 80 is mounted between said plates 76 and 78 wherebysubstantially parallel fluid passageways 82, 84, 86 and 88 are defined.Flanges 90 are mounted at the ends of plates 76 and 78 and perform thesame function as flanges 30 and 60 described above. The cooperationbetween corrugated plate 80 and plates 76 and 78 serves to perform afluid impedance and damping function in the following manner: when endportion 92 is raised and end portion 94 is lowered, and the fluid inpassageways 84 and 86 begins to move toward end portion 94, saidmovement is impeded because the portions 96 of plate 80 which areclosest to plate 76 decrease the area through which the fluid can passand therefore impede its flow. Similarly, the portions 98 of plate 80nearest plate 78 reduce the area of the fluid flow and therefore impedesaid flow. The plates 76, 78 and 80 are made of substantially unyieldingmaterial, such as iron, so that the impedance imparted thereby is amaximum in accordance with the design. When the fluid mass arrives atend portion 94, the plates function to dampen the kinetic energyimparted to said mass by causing said moving mass to assume many changesof direction. Flanges 9t} and plates 76, '78 and 80 then cooperate toreduce the propagation of a reflected wave and also prevent theimmediate reversal of the fluid mass due to the then raising end portion94.

It is to be understood that the number of plates, passageways, flangesand dimensions thereof, and the number and type of corrugated plates maybe varied without departing from the spirit of the invention.

Referring now to the embodiment of the invention shown in FIGURES 9 and10, there is disclosed an elongated fluid containing means 1% having aplurality of upstanding stiffened plates 102 mounted in a verticalposition and extending substantially parallel to the longitudinal axisof said tank 100. Stiffened plates 162 are greatly corrugated and theaxes of the undulations are substantially vertically disposed. Saidstiffened plates 1G2 define a plurality of parallel liquid passagewaysthrough which the liquid within tank 1% flows in response to the roll ofthe ship as described above. It can be seen that the ends 102a and 10212of the plates are spaced from the ends of tank 160 as the liquid istransferred through the passageways defined by stiffened plates M2. Thekinetic energy thereof is dissipated due to the fluid friction impart-edby the corrugations on said plates. The operation of this system issubstantially the same as that described above.

Referring now to th embodiment of the invention shown in FIGURES 11 and12, there is provided another elongated stabilizer tank 104 and aplurality of vertically mounted stiffened plates 106 extendingsubstantially parallel to the longitudinal axis of said tank 104.stiffened plates 196 define a plurality of fluid passageways throughwhich the transferring fluid within tank 194 flows in response to theroll of the ship. Stiffened plates 166 have roughened surfaces on eitherside thereof for the purpose of imparting fluid friction to thetransferring fluid in tank 104.

Again, as the fluid flows through the passageways defined by saidstiffened plates 106, the kinetic energy of said fluid is dissipated dueto the fluid friction imparted thereto. The operation of the system issubstantially the same as that described above.

It should be further understood that the stabilizer is adapted forstabilizing other axes of the ship. Furthermore, the stabilizer is notlimited to ship installations but can be employed with other vehicles orplatforms that are subject to disturbances of the supporting medium.

Moreover, depending upon design specifications, the damping and impedingforces may be imparted to some degree by the cooperation between theplates and tank sides without the use of the fluid friction means orflanges without departing from the spirit of the invention.

While there has been disclosed what at present are considered to bepreferred embodiments of the invention, it is to be understood thatchanges and modifications can be made therein without departing from theessential spirit of the invention. It is intended therefore in theappended claims to cover all such changes and modifications within thetrue scope of the invention.

What is claimed is:

1. In combination with a ship, an elongated tank stabilizer having itslongitudinal axis extending athwartship, a body of liquid partiallyfilling said tank to a predetermined level, the top of said tank beingabove the liquid top surface to form an air space thereover, at leastone upstanding plate extending athwartship within said tank and spacedfrom the ends thereof to form Wing tanks therein, said plate togetherwith said tank forming at least two athwartship directed straight liquidpassageways of generally uniform cross section within said tank whichdirectly interconnect the wing tanks, said plate having an exaggeratedroughened surface extending generally over the entire length and heightthereof and operative to impart more damping to the movement of liquidgenerally throughout the length of the passageway, than can be derivedfrom conventionally surfaced plating.

2. A combination as set forth in claim 1 wherein a plurality of suchplates are provided within said tank each spaced from the others in thefore and aft direction and extending generally parallel with the longdimension of the tank, so as to form a plurality of straight anduniformly cross sectioned passageways.

3. The combination as set forth in claim 2 wherein each said plate hastwo opposite roughened surfaces substantially throughout defining thebounds of the respective passageways.

4. The combination as set forth in claim 3 wherein each roughenedsurface comprises highly corrugated surfaces, each corrugation extendingsubstantially vertical.

References Cited UNITED STATES PATENTS 3,155,066 11/1964 Field 114125FOREIGN PATENTS 731,246 2/ 1943 Germany.

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner.

